1. Field of the Invention
The present invention relates to a process for the embedment or containment of waste materials, especially of radioactive waste materials, by the embedding or containment thereof in a ceramic matrix through the intermediary of the chemical precipitation of a hydrosol of the matrix, which is formed through the reaction of a nitrate with ammonia or ammonium hydroxide. In the process, the hydrosol is trickled in a pouring column into a precipitation bath, subsequent to the introduction of the material which is to be embedded, in which the hydrosol particles which are formed during the trickling gelatinize into gel particles. The gel particles are removed from the precipitation bath, washed, dried and finally sintered.
2. Discussion of the Prior Art
The above-described process is known, in particular, for the containment or embedding of wastes which contain radioactive materials. The wastes are embedded in this manner in a resistant or high-strength ceramic matrix, which prevents any egress of the noxious materials into the biosphere. This process is described in Jul-Conf-42 (Vol. 1) June 1981, ISSN 0344-5798, "Proceedings of the International Seminar on Chemistry and Process Engineering for High-Level Liquid Waste Solidification". For the containment of the radioactive waste materials it is possible to proceed from the Sol/Gel-process with internal gelatinizing, having reference to the article in the above-mentioned publication by W. J. Lackey, et al., "Sol-Gel-Derived Waste Forms", page 350 et seq; whereas with the utilization of more stable starting solutions, there is also employable the external gelatinizing; for example, by referring in the same publication to the article by E. Zimmer, "Fixing of HAW- and TRU-Waste uber ein Sol/Gel-Verfaren", page 338 et seq. In the last mentioned process, hydrosols are produced from aqueous solutions of nitrates of the radioactive waste materials and aluminum nitrate under the addition of ammonia. Thereby, for the formation of the hydrosol, there is initially carried out only a part of the precipitation reaction EQU Al(NO.sub.3).sub.3 +3NH.sub.4 OH.fwdarw.Al(OH).sub.3 +3NH.sub.4 NO.sub.3,
as a result of which there are produced viscous, readily tricklable hydrosols. In the second process step, the hydrosol is then trickled into a precipitation bath which is constituted of an aqueous ammonia solution. Thereby, the precipitation reaction is terminated, and from the hydrosol droplets there are formed gel particles. The gel particles contain ammonium nitrate from the precipitation reaction, which is removed in a washing step after the removal of the gel particles from the precipitation bath. However, during this washing, a part of the introduced materials will again dissolve, so that during the embedding of radioactive waste materials, for example, cesium is quantitatively encountered in the wash water. As a consequence, prior to the discharge of the washing water into waste water or effluent drainages, there is required a cleansing and removal of the radioactive materials entrained therein.